The invention refers to an apparatus for the preparation of preforms to be used in manufacturing plants provided for the production of bottles and containers or products of various kind, such an apparatus being adapted to prepare the preforms in a manner that is not only quick, but also different from the traditional one, in view of the subsequent utilization of said preforms for the production of said products therefrom.
Plants for producing bottles and containers of various kind through the use of plastic materials such as PET, PEN and thermoplastic materials of various kind are generally known in the art to substantially comprise a preform forming station that is formed by at least a machine tool such as for instance a screw extruder, into which the plastic material is fed in pelletized form for being first heated up to its melting temperature, or melt point, and then injected by means of moulding presses through injection conduits communicating with moulds formed by a group of cavities and a group of plungers, or punches, thereby filling the various cavities of each such mould in view of in this manner forming respective preforms to be eventually used for the production of the above cited containers or bottles.
These plants further comprise stations in which the so moulded preforms are sequentially allowed to cool down to temperature values below the melting temperature of the respectively used thermoplastic materials, are allowed to stabilize at the respectively reached temperature, and are finally subjected to a blow moulding process, in which moulding tools and equipment of a traditional type are generally used, in view of thereby producing the bottles or containers to the desired shape and size, wherein said bottles or containers are finally ejected from the plant in a traditional manner and packaged for shipment to the customers.
In the plants of the above mentioned kind, the moulds that are currently used in the above cited preform forming phase are displaced, during the moulding phase, in that the group of plungers or punches, which are generally movable, are caused to move against the group of cavities, which are generally of the stationary type, during the mould clamping phase, whereas, at the end of the moulding cycle, said group of plungers or punches are temporarily moved away from said group of cavities in order to enable the so formed preforms to be removed from said group of cavities and undergo the subsequent cool-down and temperature stabilization phases preceding the final blow moulding of the same preforms into the final products, ie. bottles or containers of various kind, after which the above cited groups of plungers or punches and cavities of the preform forming moulds are again moved against each other for a new preform forming cycle.
This sequence of opening and clamping movements of the moulds, along with the accompanying preform cool-down phases, unavoidably brings about a certain extent of downtime during which the same moulds are practically idle and the molten plastic mass cannot be injected thereinto. On the other hand, said moulds cannot be provided with sizes that are in excess of well defined limits, in view of being able to increase the number of their cavities and, therefore, the number of pieces that can be produced in each moulding cycle, since such an oversizing would unavoidably make it much more complicated, if not even impossible, for said moulds to be handled in their opening and clamping movements representing the actual circumstances in which the overall operating times are relatively long and determine productivity levels that cannot be improved any further.
It therefore is a purpose of the present invention to do away with the drawbacks and the limitations deriving from the use of the present, prior-art tools and plants for moulding bottles and containers of various kind, by providing a preform preparation apparatus for bottle or container manufacturing plants which is so designed as to be able to significantly increase the output capacity of said moulds and plants during each moulding cycle thereof, while making use of normally sized moulds provided with a same number of moulding cavities as the moulds that are currently used for the same task.